Catalytic cracking, catalytic schizolysis and heavy oil catalytic schizolysis technology is the key technology of the oil refining, catalytic schizolysis is classified into the catalytic schizolysis of wax oil and the catalytic schizolysis of heavy oil. The generated oils produced from these processes are collectively called catalytic hydrocarbons. Through the processing & handling, generally fractionation with fractionation fractionator, the obtained catalytic hydrocarbons can be fractionated into the products such as dry petroleum gas, liquefied petroleum gas, gasoline, diesel oil and heavy oil etc. Among them, the gasoline and diesel oil occupy above 70% of the supply volume of the gasoline and diesel oil in the market.
As the environmental protection requirements become more and more strict, the standard of gasoline & diesel oil will be increased continuously. The current processing method wherein the catalytic hydrocarbons go through the fractionator has the following shortcomings: the first is that the quality of the produced gasoline and diesel oil should be improved, the alkene content is too high, octane value (RON) is too low, the cetane number of the diesel oil is too low, the stability does not conform to the requirements. The second is that the above processing method can not produce multiple grades of gasoline simultaneously, in addition, there is only one product type. The third is that the proportion between produced gasoline and diesel oil does not conform to the market need, the diesel oil can not satisfy the need, whereas the gasoline is in oversupply status.
In order to solve the above problem, Chinese patent with patent No. 03148181.7 namely “treatment method of catalyzing the hydrocarbon recombination” has provided a type of treatment method of catalyzing the hydrocarbon recombination, furthermore, the Chinese patents with patent No. 200310103541.9 and 200310103540.4 have given publicity to the improved patents concerning the water rinsing system and solvent recycling, however, the methods of reducing sulfur and olefin have not been touched upon in these publicized patents.
The current GB17930 gasoline standard requires that the sulfur content is below 0.05% (wt), the olefin content is below 35% (v) and the benzene content is below 2.5% (v). Most of the refineries can assure the quality of the gasoline. However, the National Gasoline Standard III that will be implemented in 2010 requires the following: the sulfur content is below 0.015% (wt), the olefin content is below 25% (v) or even lower and the benzene content is below 1% (v). For most of the refineries, they must be confronted with the requirements of higher standard, i.e., the National Gasoline Standard IV: the sulfur content is below 0.005% (wt), the olefin content is below 25% (v) or even lower. Gasoline quality solution must consider the transition from National Gasoline Standard III to National Gasoline Standard IV. The better planning is to follow National Gasoline Standard IV in single step.
Since the proportions of blended components in the gasoline products of our country differ greatly with those of the developed countries, the catalytic cracking gasoline (hereafter called catalytic gasoline) occupies a high proportion while reformed gasoline and gasoline alkyl ate only occupies a little proportion. Furthermore, this condition will exist for a long time. Therefore, the method of reducing sulfur and olefin mainly touches upon the problem of catalyzed gasoline.
It is generally acknowledged that 5-10% of the general sulfur in the catalytic cracking material will enter the gasoline fraction. According to the characteristics of the refineries in our country that catalytic material hydrogenation purification capability is low, secondary processing catalytic cracking capability is high and there is residual oil coking, the sulfur content of the catalytic gasoline in the refinery processing the crude oil with low sulfur content (sulfur content 0.3%) is about 200 ppm, if the crude oil with sulfur content of 0.8%, the sulfur content of the catalytic gasoline is about 900 ppm. Therefore, the difficult point in the upgrade of gasoline quality has changed from the problem of olefin to the problem of sulfur. It is impossible to radically solve the problem of sulfur through the improvement of catalytic cracking process or catalyst. The catalytic cracking material hydrogenation and desulfurization cannot be applied in large scale due to big investment, high operation cost and current condition in the refineries. Furthermore, it is inapplicable to the refineries processing rude oil with low sulfur content. In the meantime, the catalytic cracking equipment excessively reduces the olefin; therefore, it will aggravate the loss of benzoline and the octane number (RON) of the gasoline.
Therefore, it is a technical problem that how to provide a system for blended gasoline having low sulfur content, low olefin content and high octane number (RON) with low cost.